1. Field of the Invention
The present invention relates to a single component development device and a process cartridge using the single component development device.
2. Discussion of the Background
There are two types of dry development methods adopted in electrophotography. One is a system in which a two component developing agent including a toner and a carrier is used and the other is a system in which a single component developing agent including a toner without a carrier is used. In recent years, the method using a single component developing agent has been popular for a low end laser printer in terms of size reduction. In the case of a single component development device, there is a widely adopted system in which a thin layer forming member is provided facing a development roller to regulate the layer thickness of the toner transferred on the surface of the development roller and charge the toner by pressing the toner when the toner passes through the thin layer forming member.
However, there is a problem to this method, which is the driving torque of the development roller increases due to the friction between the layer thickness forming member and the development roller. In addition, when the regulation pressure to the toner is set from about 25 to about 60 (N/m) to relieve the friction between the thin layer forming member and the development roller, the toner attached to the nipping portion of the thin layer forming member where the toner is nipped by the thin layer forming member and the development roller tends to be hardly transferred, which leads to a fixation problem.
Taking into account such a background, there is a technology which describes a non-magnetic single component development device that suitably maintains the charging property and the fluidity property of toner without deterioration even when the attachment state of external additives of the single component developing agent (i.e., toner) varies due to the load by a layer thickness regulating member (thin layer forming member), thereby stably producing quality images. This toner includes a particular charge control agent {(bis-[3,5-di(t-butyl)salicylate]boron (III) potassium)} to prevent deterioration of the charging property and the fluidity property caused when the toner passes through the layer thickness regulating member. However, there is no description about the regulating pressure between the layer thickness regulating member and the development roller or dispersion of a charge control agent in the non-magnetic single component development device. Thus, it is difficult to prevent fixation of toner on the development roller and reduce the driving torque of the development roller.
There is another technology which describes a development device which relieves the driving force and elongates working life of an image bearing member by setting the ten point height of irregularities (Rzjis) of the development roller in a range of from 20 to 50 μm and the gap between the development roller and the image bearing member in a range of from 150 to 400 μm. However, since this development device has a large Rzjis, the surface state of the development roller greatly changes by the friction with the thin layer forming member, which makes it difficult to maintain producing quality images for an extended period of time.